Little question about Tutorial : Defining subdomains for different materials by Dokken, if we add Neumann BC

variational formulation
1

Hello,

i just have a little question about the tutorial Defining subdomains for different materials by J.S.Dokken,

if we had a Neumann BC the third equation becomes -du/dn = g , instead of =0.

Now, do we have to add k (k=’kappa’ being the materials properties defined in the tuto, that are space distributed)

and get something like : - k du/ dn = g ?

that’s what i found using Integral by parts, but I can’t find an answer on the net on this particular set of Neumann + different material.

Thanks for reading

2

actually found out that yes it’s -k du/dn = g . and we can just use something like L = inner (g,v) ds.

Thx